JPH0766380A - Solid-state image sensing device - Google Patents

Abstract

PURPOSE:To reduce local leak current paths, by forming a photoconductive film of an amorphous silicon based film, and annealing said film by using heat and an energy beam. CONSTITUTION:A signal charge storing part 11, a signal charge reading part 14a, and a signal charge transferring part 12 are formed on a semiconductor substrate 10. A picture element electrode 19 connected electrically with the signal charge storing part 11 is formed in the uppermost layer. Thus a solid- state image sensing element chip 20 is constituted. Thereon a photoconductive layer 30 is formed, on which a transparent electrode 40 is formed. As to the photoconductive layer 30, the following are laminated in order from the solid- state image sensing element 20 side; a hydrogenated amorphous carbide layer (a-SiC:H) 31, a hydrogenated amorphous silicon layer (a-Si:H) 32, and an amorphous silicon carbide layer (a-SiC:H) 33. After that, the photoconductive film 30 is anealed by using heat and an energy beam. Thereby leak current paths caused by a lot of defects in the a-Si based film which are generated in the vicinity of the step-difference part of the picture element electrode 19 are reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoconductive film laminated type solid-state image pickup device using amorphous silicon as a photoelectric conversion film.

[0002]

2. Description of the Related Art Amorphous silicon (a-Si) shows a good semiconductor property when it is alloyed with hydrogen atoms, because the Si dangling bonds in the film are compensated by hydrogen atoms. It is known that it can be formed into a film and has high photoconductivity. Utilizing this feature, it is widely used in semiconductor devices such as solar cells, stacked solid-state imaging devices, liquid crystal displays using thin film transistors (TFTs), and contact sensors.

However, when a steep step or foreign matter such as dust is present on the substrate, a grows on it.
-Si-based film (for example, a-Si: H, a-SiC: H, a
-SiN: H, a-SiGe: H and a-containing microcrystals
Homogeneous growth of Si (μc-Si) film, etc. is hindered,
Strain is applied to the Si network in that portion. As a result, the Si-Si bond length of that portion is 0.235n which is a normal value.
The state is extended from m, and many defect levels are generated in the forbidden band of the a-Si layer.

When many defects are present in a-Si, a leak current easily flows in a local portion thereof due to a mechanism such as hopping conduction. That is, when a steep step portion or a foreign substance is present on the substrate, a leak current path is easily formed in the a-Si based film portion in the vicinity thereof, which is a cause of lowering the performance of the semiconductor device and lowering the yield. Was becoming.

On the other hand, the photoelectric film stack type solid-state image pickup device uses a conventional solid-state image pickup element as a basic chip, and a photoconductive film and a transparent electrode are stacked on the basic chip, so that the aperture ratio of the photoelectric conversion portion can be increased. It has characteristics. A as a photoconductive film
In the formation of the photoelectric conversion part using -Si, a-Si and a material having a band gap larger than that of a-Si, such as amorphous, are used for the purpose of preventing injection of carriers from the transparent electrode and not deteriorating conversion efficiency. A bond with a material such as silicon carbide (a-SiC) is formed. a
The photoelectric conversion part made of a combination of -Si and a-SiC materials includes a-SiC (n) / a-Si (i) / a-SiC (p),
SiC (i) / a-Si (i) / a-SiC (p), a-Si (i) / a-SiC (p), etc. have been reported. In this notation, (i), (n),
(P) represents i type, n type, and p type, respectively. To form the n-type and the p-type, for example, phosphorus (P) and boron (B) are doped, respectively.

The role of the a-SiC (p) layer in these structures has a role as a window material for transmitting incident light and a role for blocking injection of carriers from the transparent electrode. In the actual operation of the device, the transparent electrode side is negatively biased, and therefore, for the latter purpose, the performance of blocking the injection of electrons must be provided. In fact, the p-type is used to prevent injection of electrons, but it is considered necessary to increase the B doping concentration in order to improve the performance.

Conventionally, the mercury-sensitized CVD method and the plasma CVD method have been applied to the formation of the a-SiC (p) layer. When the mercury-sensitized CVD method is used, the B doping concentration for the p-type has been about 0.25% with respect to the sum of the numbers of Si and C atoms. However, it has been pointed out that organic mercury may be generated in the reaction chamber when the a-SiC layer is formed by using the mercury-sensitized CVD method, and it has been considered that the formation by the same method is not preferable. Therefore, the plasma CVD method is desired when forming the a-SiC (p) layer. However, when the a-SiC (p) layer is formed by the plasma CVD method, if the B doping concentration is set to about 0.25%, the leak dark current becomes large, and a minute white color when an element is operated is obtained. This caused a new problem of causing scratches.

Further, in the photoconductive film laminated type solid-state image pickup device, signal charges photoelectrically converted in the a-Si layer are collected,
In addition, a refractory single metal such as Ti or Mo has been used as a pixel electrode material that plays a role of transmitting to the storage diode. The reason is that the a-Si layer is generally deposited at a substrate temperature of 200 to 300 ° C., but using a high melting point material for the pixel electrode can prevent contamination of the a-Si layer by diffused metal atoms.

However, when a high melting point metal such as Ti or Mo is used for the pixel electrode, a problem arises in that the leak dark current during device operation cannot be sufficiently reduced. If the leak dark current is not sufficiently small, dark current unevenness of the image output from the solid-state imaging device, that is, fixed pattern noise will occur. The cause is that a reverse bias is applied to the diode of the a-Si layer during device operation, but in that case, hole injection from the pixel electrode to the a-Si layer is not effectively blocked. Was found as a result of analysis of current-voltage characteristics.

[0010]

As described above, conventionally, when a steep step or a foreign substance is present on the substrate, a
The conventional method of only growing a -Si layer is to use a-Si
Since it is difficult to prevent a leakage current path from being formed in the layer, there are problems such as a decrease in performance of the solid-state imaging device and a decrease in manufacturing yield.

Further, in the laminated solid-state image pickup device, the a-SiC (p) layer used in the photoelectric conversion portion plays a role of blocking injection of electrons from the transparent electrode, but enhances its performance. For this purpose, the B doping concentration is 0.25%,
Alternatively, higher doping conditions have been used. Under such conditions, plasma C free from mercury contamination
When the a-SiC (p) layer is formed by the VD method, there is a problem that a leak dark current is large and a minute white flaw is generated during the operation of the element.

Further, when a simple refractory metal such as Ti or Mo is used for the pixel electrode of the stacked solid-state image pickup device, hole injection from the pixel electrode to the a-Si layer diode cannot be effectively blocked during operation. Therefore, there is a problem that the leak dark current is not sufficiently reduced and fixed pattern noise (dark current unevenness) occurs.

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a high-performance and high-yield solid-state imaging device in which a local leak current path in the a-Si layer is reduced. To provide.

Another object of the present invention is a-SiC.
An object of the present invention is to provide a solid-state imaging device capable of preventing injection of electrons from a transparent electrode and reducing leak dark current by optimizing the doping condition of the (p) layer.

Still another object of the present invention is to provide a solid-state image pickup device capable of sufficiently reducing leak dark current during device operation and having improved fixed pattern noise characteristics.

[0016]

In order to solve the above problems, the present invention employs the following configurations. That is, according to the present invention (Claim 1), a signal charge storage portion, a signal charge read portion, and a signal charge transfer portion are formed on a semiconductor substrate, and a pixel electrode electrically connected to the signal charge storage portion is formed on the uppermost layer. In the solid-state image pickup device of the photoconductive film stack type including the formed solid-state imaging device chip, the photoconductive film formed on the solid-state imaging device chip, and the transparent electrode formed on the photoconductive film, The conductive film is formed of an amorphous silicon-based film, and in order to reduce the number of local leakage current paths, the amorphous silicon-based film is annealed using heat and an energy beam. To do.

Here, it is desirable to use, as the energy beam, light containing a wavelength component having an energy not less than the band gap of the amorphous silicon film. In addition, the present invention (Claim 2) forms a signal charge storage part, a signal charge reading part, and a signal charge transfer part on a semiconductor substrate, and has a pixel electrode electrically connected to the signal charge storage part on the uppermost layer. In the solid-state image pickup device of the photoconductive film stack type including the formed solid-state imaging device chip, the photoconductive film formed on the solid-state imaging device chip, and the transparent electrode formed on the photoconductive film, A conductive film is formed on at least two layers having a junction between amorphous silicon on the solid-state imaging device chip side and p-type amorphous silicon carbide on the transparent electrode side, and the doping concentration of boron into the amorphous silicon carbide is determined by the number of silicon and carbon atoms. Is set to 0.1% or less with respect to the sum of

Here, it is desirable that the p-type amorphous silicon carbide layer is grown by a plasma CVD method free from mercury contamination. Further, the p-type dopant is not necessarily limited to boron, and other impurities can be used.

Further, according to the present invention (claim 3), a signal charge accumulating portion, a signal charge reading portion and a signal charge transferring portion are formed on the semiconductor substrate, and the uppermost layer is electrically connected to the signal charge accumulating portion. A solid-state image sensor chip having a pixel electrode formed thereon;
In a photoconductive film stack type solid-state imaging device including a photoconductive film formed on the solid-state imaging device chip and a transparent electrode formed on the photoconductive film, at least the photoconductive film of the pixel electrode is in contact with the photoconductive film. The surface layer is formed of TaC, TaN, ZrC or ZrN.

[0020]

In the present invention (Claim 1), a normal Si-Si bond length is present in the vicinity of a step or a foreign substance, that is, in a steep step or a foreign substance of the underlying substrate, that is, in an a-Si film formed on the unevenness. Many expanded Si-Si bonds are generated. Then, the expanded Si—Si bonds generate a large number of defect levels at the valence band edge and the conduction band edge in the Arbach tail portion in the forbidden band of the a-Si film. These stretched Si-Si bonds (weak Si-Si
Since the bond energy of bond is as small as about 1.6 to 1.7 eV, the forbidden band width (1.5 to 2.
The electron-hole recombination energy excited at the conduction band edge and the valence band edge by irradiation with an energy beam containing an energy component of 3 eV) or more is easily broken.

In the present invention, the a-Si system film is irradiated with the energy beam by utilizing the above mechanism, so that the weakly stretched weak Si-Si bond is broken and the thermal annealing is performed during the irradiation of the energy beam. The feature is that the broken Si network is reconstructed into a strong Si-Si bond having a large bond energy by applying a treatment. As a result, local leak current paths due to a large number of defects in the a-Si-based film generated in the vicinity of the irregularities of the base substrate are reduced, and the performance and yield of the solid-state imaging device can be improved.

According to the present invention (claim 2), a-
The doping concentration of B in SiC (p) is 0.01%
By suppressing below, a-SiC
Since the Zener breakdown at the (p) / a-Si (i) interface can be efficiently suppressed, the leak dark current can be suppressed to be small, and the occurrence of minute white scratches during the operation of the element can be suppressed. .

In the present invention (claim 3), Ta
Metal carbide or metal nitride layers such as C, TaN, ZrC and ZrN can be deposited by sputtering or CVD, or by C,
Although it is formed by a heat treatment method in a gas atmosphere containing N atoms, the carbon content and the nitrogen content can be controlled with good reproducibility within a range of 0 to 80% by controlling the film forming conditions. Have.

When these metal carbides and metal nitrides are used on at least the surface of the pixel electrode to stack the a-Si layer,
The contained carbon and nitrogen atoms diffuse slightly into the a-Si layer. As a result, the hydrogenated amorphous silicon film (a-Si: H), which is the a-Si layer near the pixel electrode, is a-Si: C: H or a-S doped with carbon or nitrogen, respectively.
It is considered to change to i: N: H. In that case, aS
Since i: C: H and a-Si: N: H are made wider than a-Si: H (usually optical bandgap = 1.7 to 1.8 eV), holes are injected from the pixel electrode. Will be blocked. It is expected that this effect will lead to a reduction in leak dark current, and eventually a reduction in fixed pattern noise (dark current unevenness).

In experiments conducted by the present inventors, among various metal carbides and metal nitrides, TaC, TaN, and ZrC were used.
A remarkable effect was observed when ZrN and ZrN were used as the pixel electrode material. As a reason for this, it is expected that there is a mechanism in which carbon atoms and nitrogen atoms are most easily diffused in the a-Si film among the above four materials. In addition, the above-mentioned four kinds of materials all have very low electrical resistivity of less than 200 [μΩ · m], and therefore, when used as an electrode material, there are no practical problems.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a sectional view showing an element structure of a photoconductive film laminated type solid-state imaging device according to a first embodiment of the present invention. In the figure, 10 is a p-type Si substrate, and on the surface layer of the substrate 10, an n-type layer 11 forming a storage diode (signal charge storage portion) and an n-type layer forming a vertical CCD channel (signal charge transfer portion) 12. A p-type layer 13 for element isolation is formed. Transfer electrodes 14 and 15 are formed on the n-type layer 12 via a gate insulating film. Transfer electrode 1
Part of 4 is extended to the storage diode 11, and this part serves as a read gate (signal charge read section).

An interlayer insulating film 16 is formed on the substrate 10 on which these are formed. An extraction electrode 17 is formed on the insulating film 16 so as to be in contact with the n-type layer 11 through a contact hole provided in the insulating film 16. Further, a planarizing insulating film 18 is formed on the insulating film 18.
A pixel electrode 19 is formed on top of the pixel electrode 19 so as to be in contact with the extraction electrode 17 through a contact hole provided in the insulating film 18.

A photoconductive film 30 is deposited on the solid-state image pickup device chip 20 thus constructed, and the IT film is formed on the photoconductive film 30.
A transparent electrode 40 such as O is formed. Photoconductive film 30
, Which functions as a photoelectric conversion layer, is composed of a hydrogenated amorphous silicon thin film system. Specifically, from the solid-state imaging device chip 20 side, a hydrogenated amorphous carbide layer (a-SiC: H) 31 which is a hole blocking layer, and a hydrogenated amorphous silicon layer (a which is a main photoconductive layer). -Si:
H) 32 and a p-type amorphous silicon carbide layer (a-SiC: H) 33, which is an electron block layer, are sequentially stacked. The total thickness of the photoconductive film 20 is about 1 to 2 μm.

Although the basic structure of the apparatus of this embodiment is the same as that of the conventional apparatus, in this embodiment, as will be described later, the photoconductive film is annealed by using heat and energy beams. Is different from the conventional one.

As a method for forming the photoconductive film 30, a plasma CVD method which decomposes silane gas by plasma, which is well known in the art, and a light C which decomposes by light energy are used.
The VD method may be used. In this embodiment, the photoconductive film 3
The substrate temperature when forming 0 was 230 ° C. Further, the solid-state imaging device before the annealing treatment of the photoconductive film 30 was observed with a cross-section transmission electron microscope (TEM).
A linear defect as indicated by 35 was observed in (a). This linear defect is caused by a step difference (100 to 300 n) of the pixel electrode 19.
m). When this linear defect was evaluated by the energy dispersive X-ray diffraction method (EDX method), a clear decrease in Si density was observed. That is, it can be considered that the portion where the weak Si—Si bond in which the bond is extended is formed is the linear defect of 35.

In this embodiment, after the laminated solid-state image pickup device is formed as shown in FIG. 1, the photoconductive film 30 is annealed by using heat and an energy beam. In addition, an example in which light is used as the energy beam is shown.

First, as shown in FIG. 2A, the apparatus shown in FIG. 1 is placed on a hot plate 50 whose temperature is set in an appropriate range from 130 ° C. to a film forming temperature (230 ° C. in this embodiment). The reason why the upper limit of the temperature setting is set to the film formation temperature is that if the film formation temperature is exceeded and annealing is performed, a large amount of hydrogen in the film is likely to be desorbed and a new defect may occur. After installation on the heating plate 50, white light emitted from a xenon lamp with a 500 W output was condensed by a lens and heat + light annealing was performed.

Here, the light intensity on the surface of the solid-state image pickup device is about 5.
It was W / cm ² . Simultaneous heat + light annealing time is 10
Done for an appropriate time, ranging from minutes to 300 minutes. Then, if necessary, annealing treatment was performed by heat alone for a time in the range of 15 minutes to 60 minutes. In addition, in this embodiment, the light is continuously irradiated during the annealing, but the light may be irradiated as pulsed light by using a chopper or the like.

As a result of observing the solid-state image pickup device thus annealed by heat + light with a cross-section TEM, FIG.
As shown in, it was found that 35 linear defects almost disappeared.

Next, in order to examine the effect of this embodiment, a negative potential is actually applied to the transparent electrode 40, that is, a reverse electric field is applied to the photoconductive film 30, and the device is operated to generate a minute white defect on the display. I checked the situation. The minute white defect is generated when the local leak current of the photoelectric conversion layer is large.

FIG. 3 shows the measurement results of minute white flaws in comparison with the conventional example. The horizontal axis in FIG. 3 represents the magnitude of the electric field applied to the photoelectric conversion layer, and the vertical axis represents the number of minute white scratches on the display. As shown in the figure, it is clear that this embodiment is more heat +
The number of minute white scratches is extremely smaller than that in the conventional example in which the optical annealing is not performed, when compared with the same electric field. That is, the local leak current is remarkably reduced in the area of the device of this embodiment.

In the solid-state image pickup device of this embodiment, it is desirable that the reverse electric field applied to the photoelectric conversion layer is large in order to reduce the photoconductive afterimage caused by the a-Si layer. However,
As shown in the conventional example of FIG. 3, when the electric field becomes large, minute white scratches are generated, so that an electric field of 3 × 10 ⁴ V / cm or less has been usually used. According to the device configuration of the present embodiment, as described above, even if the electric field is increased, the occurrence of minute white scratches is reduced, so that the afterimage can be further reduced and high performance can be realized.

In the above, the case where there is a step on the base substrate has been described, but the same applies when foreign matter such as dust adheres to the base substrate. The point is that even if an a-Si layer is formed on a base substrate having irregularities, the number of local leak current paths, that is, the number of local leak current locations, is reduced by the configuration of the present invention. This is the point of the invention.

The present invention is not limited to the solid-state image pickup device, but can be applied to a semiconductor device using an a-Si layer. For example, a liquid crystal display using an a-Si TFT or an a-Si photoconductive device. It can also be applied to a contact sensor using a layer in the photosensitive portion. In either case, a high-performance and high-yield semiconductor device with few local leakage current defects can be realized.

Although the embodiments have been described mainly focusing on the Si--Si bond, different kinds of atomic bonds such as Si--G are used.
The present invention can also be applied to a semiconductor device including a thin film having a network formed of e-bond, Si-C bond, Si-N bond, or atomic bond of the same kind, for example, C-C bond.

Further, the present invention is not limited to a semiconductor device including an amorphous thin film, and is also applicable to a semiconductor device using an amorphous thin film containing microcrystals or a polycrystalline film (for example, a polycrystalline Si film). It goes without saying that the invention can be applied. (Embodiment 2) Next, a second embodiment of the present invention will be described. In this example, a-SiC used as a photoconductive film was used.
The doping concentration of the (p) layer is optimized. The device structure is similar to that shown in FIG. 1, and the photoconductive film 30 has a structure of a-SiC (i) / a-Si: H.
(I) / a-SiC: H (p) was adopted.

In this structure, the film thickness of each layer was 20 nm, 1.8 μm and 20 nm, respectively. In addition, as a method of forming each layer, a-SiC: H (i), a-Si
Plasma CVD method for the C: H (p) layer, and a-S
A mercury-sensitized CVD method was used for the i: H layer.

FIG. 4 shows current density-voltage characteristics when a reverse bias is applied to the a-Si layer diode. A curve A shown in the figure shows the case where the B doping concentration of the a-SiC: H (p) layer is 0.25%, while a curve B shows the case where the B doping concentration is 0.1%. As is clear from this figure, by setting the B doping concentration to 0.1%, it is possible to suppress the generation of the current during reverse bias, that is, the leak dark current.

In order to clarify the effect of the B doping concentration of the a-SiC: H (p) layer on the leak current during reverse bias, the B doping concentration is plotted on the vertical axis and a reverse bias of 10 V is applied. FIG. 5 shows the leak dark current on the vertical axis. As can be seen from the figure, the leak dark current increases when the B doping concentration is higher than 0.1% and lower than 0.01%. It is considered that the reason why the leak dark current increases when the B doping concentration is less than 0.01% is that the electron injection blocking performance is deteriorated.

In this embodiment, the photoconductive film 30 is used.
A-SiC (i) / a-Si: H (i) / a-Si
Although the three-layer structure of C: H (p) is used, the a-SiC: H (i) layer as the hole blocking layer 31 is a-SiC: H.
It may be a layer (n), or may be omitted. (Embodiment 3) Next, a third embodiment of the present invention will be described.

FIG. 6 is a sectional view showing the element structure of the photoconductive film laminated type solid-state image pickup device according to the same embodiment. The same parts as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

Although the basic structure is the same as that of FIG. 1, the present embodiment is different from the first embodiment in the material of the pixel electrode and is different in the laminated structure of the photoconductive film. That is,
The pixel electrode 69 is not a refractory metal film of Mo, Ti, etc., but TaC, TaN, ZrC of metal carbide or metal nitride.
Alternatively, it is made of ZrN. In addition, the photoconductive film 70 is
An a-Si: H (i) layer 72 which is a main photoconductive film and an a-SiC: H (p) layer 73 which is an electron blocking layer.
It is composed of. In FIG. 6, p ^{+ is used} as the substrate 10.
Although a p-well is formed on the mold substrate,
The p-type substrate may be used as it is as shown in FIG.

The method of forming the pixel electrode will be described in detail below. The most widely used method for producing TaC, TaN, ZrC and ZrN films is the sputtering method. One of the sputtering methods is, as is generally well known, a method in which a single metal target Ta, Zr is subjected to DC or AC sputtering in an atmosphere of N ₂ or CH ₄ . Another method is compound target Ta
This is a method of directly forming a film by sputtering from C, ZrC and ZrN. Also in this case, the sputtering atmosphere should be N ₂
Alternatively, a method of introducing CH ₄ is also widely used.

In addition to these methods, there is a method of forming a Ta or Zr thin film in advance and then compounding it by rapid heating and rapid cooling (Rapid Themal Anmeal) treatment in an N ₂ or CH ₄ atmosphere. The temperature of rapid heating differs depending on the individual material,
A range of about 500 to 1300 ° C is widely used.

A vapor phase growth (CVD) method is also widely used. In this case, there are a thermal CVD method and a plasma CVD method.
TaCl ₄ or ZrCl ₄ gas and N ₂ or C as source gas
A mixed gas of H ₄ gas may be used. Of course, N ₂ gas may be used for forming the nitride and CH ₄ gas may be used for forming the carbide.

Above, TaC, TaN, ZrC and ZrN
Although the film forming method is outlined, in the case of the solid-state imaging device of the present invention, the film thickness of the pixel electrode 69 may be in the range of 50 to 500 nm. In short, the light incident through the transparent electrode 40 is blocked by the pixel electrode 69, and the CCD of the solid-state imaging device chip 60 is
The film thickness may be such that light does not leak into the channel 12, that is, it helps prevent smear. The method for separating and forming the pixel electrode 69 may be an ordinary etching method, for example, a wet etching method or a dry etching method using a photoresist process.

After the pixel electrode 69 is formed separately, a-S
The i film 70 is formed. The a-Si film 70 is formed by a plasma CVD method, a photo CVD method, or the like, as is well known. Substrate temperature is 50-500 ° C, gas pressure is 20 m
Torr to 10 Torr, hydrocarbon gas such as SiH ₄ and CH ₄ , and gas flow rate of H ₂ gas and He gas are 5 sccm
The range of ~ 5 SLM is generally used, and the decomposition energy source is usually RF (13.56 MH) in the case of the plasma CVD method.
z) high frequency power is used, but the power range is 500
In the range of ˜1 kW, in the case of the photo CVD method, an ultraviolet light source that decomposes SiH ₄ gas, for example, a low pressure mercury lamp or a deuterium lamp is used. The thickness of the a-Si film 70 is usually about 1 μm to 3 μm. ITO is usually used for the transparent electrode 40.

The dark current unevenness characteristics of the solid-state image pickup device formed as described above, that is, the fixed pattern noise characteristics, are as follows. That is, the fixed pattern noise of this embodiment using TaC as the pixel electrode was 30 el.rms, and the conventional example using Ti was 100 el.rms. In this embodiment, an example in which TaC is used for the pixel electrode has been shown, but TaN, ZrC, Zr
The fixed pattern noise is 40el.r when any of N is used.
It was less than ms, and the effect was clearly recognized as compared with the conventional one.

As described above, according to this embodiment, the pixel electrode 6
Since TaC, TaN, ZrC or ZrN is used as 9, carbon and nitrogen are slightly diffused from the pixel electrode 69 to the a-Si: H layer 72, and this serves as a hole blocking layer. Therefore, hole injection from the pixel electrode 69 to the photoconductive film 70 can be surely blocked.
It is possible to reduce the leak dark current, and thus the fixed pattern noise (dark current unevenness). Further, since it is not necessary to provide the hole blocking layer shown in FIG. 1, there is an advantage that the manufacturing process of the photoconductive film 70 is simplified.

In this embodiment, the pixel electrode 69 is entirely made of any one material of TaC, TaN, ZrC and ZrN, but the present invention is not limited thereto. At least the pixel electrode surface layer in contact with the a-Si film may be formed of any one material of TaC, TaN, ZrC, and ZrN. In this embodiment, the a-Si film is i-type a-Si: H and p-type a-S.
An example in which iC: H is sequentially laminated is shown, but it goes without saying that other laminated structures are also useful.

[0056]

As described above in detail, the present invention (Claim 1)
According to the method, annealing the heat + energy beam on the a-Si film greatly reduces the number of local leak current paths, and thus has the effect of improving the performance and improving the manufacturing yield.

According to the present invention (claim 2), a-
Blocking electrons from the transparent electrode by the SiC (p) layer and Zen at the a-SiC (p) / a-Si (i) interface
By suppressing the er breakdown at the same time, the leak dark current is suppressed, so that the occurrence of minute white scratches during the operation of the element can be suppressed.

According to the present invention (claim 3), the surface layer in contact with the a-Si film of the pixel electrode is made of TaC, TaN, Z.
By using one of the materials rC and ZrN, it is possible to greatly reduce the dark current unevenness of the photoconductive film stack type solid-state imaging device, that is, fixed pattern noise.

[Brief description of drawings]

FIG. 1 is a sectional view showing an element structure of a solid-state imaging device according to a first embodiment.

FIG. 2 is a schematic diagram showing a state before and after annealing of the photoconductive film in the first example.

FIG. 3 is a characteristic diagram showing the relationship between the electric field strength applied to the photoelectric conversion layer and the number of minute white scratches.

FIG. 4 is a view for explaining a second embodiment, and
The figure which shows the current density-voltage characteristic at the time of applying a reverse bias to i film.

FIG. 5 is a characteristic diagram showing a relationship between a B doping concentration of an a-SiC: H (p) layer and a leak dark current when a reverse bias is applied.

FIG. 6 is a sectional view showing an element structure of a solid-state imaging device according to a third embodiment.

[Explanation of symbols]

 10 ... p-type Si substrate 11 ... n-type layer (signal charge storage part) 12 ... n-type layer (signal charge transfer part) 13 ... p-type layer (element separation layer) 14, 15 ... transfer electrode 14a ... read gate part ( Signal charge reading section) 16 ... Interlayer insulating film 17 ... Extraction electrode 18 ... Planarization insulating film 19, 69 ... Pixel electrode, 20, 60 ... Solid-state imaging device chip 30, 70 ... Photoconductive film 31 ... a-SiC: H (I) Layer 32, 72 ... a-Si: H (i) layer 33, 73 ... a-SiC: H (p) layer 40 ... ITO film (transparent electrode)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hisanori Ihara, 1 Komukai Toshiba Town, Saiwai-ku, Kawasaki City, Kanagawa Prefecture, Corporate Research & Development Center, Toshiba Corporation (72) Inventor ▲ Motai ▼ Takako, Kawasaki City, Kanagawa Prefecture Komukai Toshiba Town No. 1 Incorporated company Toshiba Research & Development Center (72) Inventor Yoshiki Ishizuka Komukai City, Kawasaki City Kanagawa Prefecture Komu Toshiba No. 1 Incorporated Company Toshiba Research and Development Center (72) Inventor Akihiko Furukawa Kanagawa Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Toshiba Research & Development Center, Ltd. (72) Inventor Yoshinori Iida Komukai-shishi-cho, Saiwai-ku, Kawasaki, Kanagawa 1st, Toshiba Research & Development Center

Claims (3)

[Claims] 1. A solid-state image sensor chip having a semiconductor substrate on which a signal charge storage portion, a signal charge read portion, and a signal charge transfer portion are formed, and a pixel electrode electrically connected to the signal charge storage portion is formed on the uppermost layer. And a photoconductive film formed on the solid-state imaging element chip and a transparent electrode formed on the photoconductive film, wherein the photoconductive film is amorphous. A solid-state imaging device, which is a high-quality silicon-based film and is annealed by using heat and an energy beam in order to reduce the number of local leakage current paths. 2. A solid-state image sensor chip having a semiconductor substrate on which a signal charge storage portion, a signal charge read-out portion, and a signal charge transfer portion are formed, and a pixel electrode electrically connected to the signal charge storage portion is formed on the uppermost layer. And a photoconductive film formed on the solid-state imaging element chip, and a transparent conductive film formed on the photoconductive film, wherein the photoconductive film is a solid-state image pickup device. It has a junction between amorphous silicon on the side of the imaging device and p-type amorphous silicon carbide on the side of the transparent electrode, and the doping concentration of boron into the amorphous silicon carbide is 0.1 with respect to the sum of the numbers of atoms of silicon and carbon. % Of the solid-state imaging device. 3. A solid-state image sensor chip having a semiconductor substrate on which a signal charge storage portion, a signal charge read-out portion, and a signal charge transfer portion are formed, and a pixel electrode electrically connected to the signal charge storage portion is formed on the uppermost layer. And a photoconductive film formed on the solid-state imaging device chip and a transparent electrode formed on the photoconductive film, wherein the pixel electrode is at least the pixel electrode. A solid-state imaging device, wherein a surface layer in contact with the photoconductive film is formed of TaC, TaN, ZrC or ZrN.